Dual channel nutating waveguide feed



June 4, 1968 P. H. MOUNTCASTLE ET Al. 3,387,303

DUAL CHANNEL NUTATING WAVEGUIDE FEED Filed March 5, 1965 i ff United States Patent O 3,387,303 DUAL `CHANNEL NUTATING WAVEGUIDE FEED Paul H. Mountc'astle, Glen Burnie, Md., and William E.

Snyder, Webster, N.Y., assignors, by mesne assignments,

to the United States of America as represented by the Secretary of the Navy Filed Mar. 5, 1965, Ser. No. 437,613

3 Claims. (Cl. 343-758) ABSTRACT OF THE DISCLOSURE A Adual channel scanning device having first and second waveguides positioned in a first 'bushing in a stationary housing and third and fourth waveguides each having one end positioned in a second bushing mounted in a rotatable housing with the other ends of said third and fourth waveguides being mounted in an offset end Iof said rotatable housing, and a universal joint connecting said first and second bushings whereby rotation of said rotatable housing causes said third and fourth waveguide to be nutated.

The present invention relates to :an antenna and more particularly to compact dual ch-annel nutating waveguides for use ina parabolic microwave antenna.

The present invention provides compact dual channel waveguides including a dual nutating choke joint. A rotating-waveguide housing is provided that has an offset end in which a bearing is mounted to provide an eccentric mount. A dual channel waveguide is provided, and

` one end of the dual channel waveguide is mounted in the eccentrically mounted bearing. The other end of the dual channel waveguide is provided with a specially designed waveguide joint which is mounted in a `universal joint to allow mutation.

It is therefore a general object of the present invention to provide an improved scanning dev-ice for a radar.

Another object of the present invention is to provide compact dual channel nutating waveguides for use with a parabolic microwave antenna.

Other objects and advantages lof the present invention will be readily appreciated as the same becomes better understood by referen-ce to the following detailed description when considered in connection with the accompanying drawing wherein:

FIGURE 1 is a partial sideview of a nutating waveguide assembly, partially lbroken away to show parts in section;

FIGURE 2 is a sectional view showing a dual channel waveguide joint;

FIGURE 3 is a perspective view, partially lbroken away, showing a universal joint; and

FIGURE 4 is an exploded view of the universal joint shown in FIGURE 3.

Referring now to FIGURE 1 of the drawing, there is shown a stationary housing to which there is rotatably mounted a rotatable waveguide hou-sing 11 which is provided with yan offset end 12. A lbearin-g 13 is mounted in offset end 12 and a bushing 14 is mounted in the inner 3,387,303 Patented June 4, 1968 ice race of bearing 13. A pair of rectangular waveguides 15 and 16 are positioned in bushing 14. One end of waveguide 15 is positioned in close proximity to waveguide 17, and one end of waveguide 16 is positioned in close proximity to waveguide 18. Waveguides 17 and 18, which are rectangular :and similar in 4cross-section to waveguides 15 and 16 are stationarily mounted in stationary housing 10.

As best shown in FIGURES 2, 3, and 4 of the drawing, one end of each of waveguides 15 and 16 are connected to stationary housing 10 through a universal joint 21. Bearing member 22 of universal joint 21 is pivotally connected to bushing 23, which supports .the stationary waveguides 17 and 18. Bushing 24, which supports one end of waveguides 15 and 16, is also pivotally connected to 'bearing member 22. By way of example, 'bearings 25-28 are provided in bearing member 22 and short shafts 31 and 32, which are attached to bushing 23, are fitted in the lbores of the inner races of bearings 25 and 26, respectively. Likewise, short shafts 33 and 34, which are att-ached to bushing 24, are fitted in the bores of the inner races of bearings 27 and 28.

Referring particularly to FIGURE 2 of the drawing, there is shown the RF joint configuration for the broad wall of the rectangular waveguides. It is not necessary to choke the narrow wall. The distance 'between the station- -ary waveguides and the nutating wavegui-des is shown to be equal to the distance a. It has been determined by experimentation -that the optimum value for a is given by the following fonmula:

a=-- tan a where C is the distance between the pivot point and the outside edge of the waveguides and a is the offset angle. Bushing 23, which ho'lds stationary waveguides 17 and 18, is provided with two en'd flanges 35 and 36 and a center ange 37. Likewise, bushing 24, which holds nutating waveguides 15 and 16 is provided with two end flanges 38 and 39 and a center ange 41. The length of the flanges is shown as b, which is equal to a quarter waveL length and, therefore, would change depending upon what frequency band coverage is desired. Center flanges 37 and 41 serve as a center choke and greatly limit any undesired cross coupling. By adding absorbing material 42 to the center flange 37, cross coupling can be reduced even further.

In operation, when waveguide housing 11 is rotated, waveguides 15 and 1-6 .are nutated to transcribe a cone in space with the universal joint pivot point as the vertex and the offset angle as one half the included cone angle. The nutating waveguides a-re prevented from rotating 'by universal joint 21.

It can thus -be seen that the present invention provides improved dual channel nutating waveguides for use with :a parabolic micr-owave antenna. Obviously many modifications and variations of the present invention are possible in 'the light of the above teachings. It is therefore t0 lbe yunderstood that within the scope of the appended claims, the invention may ybe practiced otherwise than as specifically described.

What is claimed is:

1. A dual channel scanning device comprising:

`a stationary housing,

first and second waveguides attached to said housing,

ya waveguide housing rotatably mounted to said stationary housing .about an aXis of rotation and having an offset end the axis of which intersects said axis of rotation,

a bearing mounted in said offset end of said waveguide housing, and

third and 4fourth waveguides each having one end mounted in said lbearing and the other ends attached 3 4 to said stationary housing through a univers-a1 joint, a second ybushing supporting said third and fourth waveone end of said third waveguide being adjacent one guides and 'having first and second end ilanges and a end of said first waveguide and one end of said center flange, said third waveguide having an end fourth waveguide being adjacent one end of said l terminating in an opening between said first end and second waveguide, an-d whereupon rotation of s-aid- 5 center flanges of said second `bushing and said fourth waveguide housing causes nutation of said third and waveguide having yan end terminating in an opening fourth waveguides. Ibetween said second end and center flanges of said 2. A dual channel scanning device comprising: second bushing, and a stationary housing, a universal joint connecting said first an-d second bushla first bus-hing attached to said housing and having first l0 ings whereby rotation of said waveguide housing and second end flanges and a center flange, causes nutation of said third and fourth waveguides. first an-d second waveguides supported by said first bushy 3. A dual channel scanning device as set forth .in claim ing, said first waveguide having an end terminating 2 where-in a strip of absorbing material is added to the in an opening between -said first end li-ange and sa-id center ange of said first bushing thereby reducing crosscenter ange and said second waveguide having an 15 coupling of energy between waveguides.

end terminating in an opening between said second t end ange and said center iiange, References Cited a waveguide housing rotatably mounted to said station tary housing about an axis of rotation and having an UNITED STATES PATENTS offset end the axis of which intersects said axis of 2,646,508 7/ 1953 Fisher 343-761 rotation, 3,312,975 4/1967 Huelskamp s 343*761 third and fourth waveguides each having one end :rotatably mounted in Said Offset end, ELI LIEBERMAN, Przmary lixaimmer.4 

